This invention relates to a key-touch state detection device for an automatic performance piano with improved accuracy in detection of a key-touch state.
As operation modes of an automatic performance piano, there are a record mode in which performance by a performer is recorded and an automatic performance mode in which an automatic performance is made in accordance with recorded performance information or performance information supplied from an outside source. For recording a performance by a performer in the record mode, it is necessary to measure the speed at which each hammer strikes a string, a time point at which a key has been depressed and a time point at which the depressed key has been released and convert these data to electric signals for subsequent necessary processing. This will be described in detail with reference to FIG. 4 below.
In FIG. 4, an automatic performance piano 71 has a keyboard including keys 73, a string striking mechanism 77 which transmits the movement of each key 73 to a hammer 75, a string 79 which is struck by the hammer 75, a damper 78 for restraining vibration of the string 79, a pedal mechanism (not shown) and a pedal drive device (not shown) for driving this pedal mechanism.
The key 73 is pivotable about a balance pin 81 and, when the key 73 has been depressed or pivoted by an upward movement of a plunger in a solenoid 83, the movement of the key 73 is transmitted to the hammer 75 and the damper 78 through the string striking mechanism 77. The damper 78 thereby is released from the string 79 and the hammer is pivoted counterclockwise as viewed in the figure to strike the string 79.
A key sensor 89 is provided under the key 73 to detect depression and release of the key 73.
A shutter 76 is secured to the hammer 75 and a hammer sensor 74 is provided within a moving range of the shutter 76. The hammer sensor 74 detects the moving speed of the shutter 76 (i.e., the moving speed of the hammer 75). A controller 96 records performance information in response to detection signals produced by the key sensor 89 and the hammer sensor 74 and drives the solenoid 83 and the pedal drive device (not shown) in response to the recorded performance information (or performance information supplied from an outside source).
FIG. 5 is a side view of an essential portion of FIG. 4. In FIG. 5, a recess is formed in the upper portion of foremost end portion 76a of the shutter 76. In the hammer sensor 74, there are provided a couple of photo-interrupters 74a and 74b with a predetermined interval therebetween.
In the above described construction, when the key 73 (FIG. 4) has been depressed and the hammer 75 and the shutter 76 are pivoted counterclockwise as viewed in the figure, the foremost end portion 76a of the shutter 76 shields light entering the photo-interrupter 74a at position C of the hammer. As the hammer 75 and the shutter 76 are further pivoted, the recessed surface 76b shields light entering the photo-interrupter 74b at position D of the hammer which strikes the string 79 at this position.
Accordingly, by measuring time from shielding of light in the photo-interrupter 74a till shielding of light in the photo-interrupter 74b, the speed of the hammer 75 at this time (i.e., time immediately before the string 79 is struck by the hammer 75) can be obtained. This speed is recorded in the controller 96 as key-touch strength.
As described above, in the prior art automatic performance piano, timings of depression and release of a key are detected by the key sensor 89 and the speed of striking of the string is detected by the hammer sensor 74.
In the prior art automatic performance piano, however, it is necessary to provide one sensor under the key and the other sensor on the hammer and this requires a number of assembling steps and, besides, requires a long time in binding wirings with resulting increase in the cost. Moreover, since the stroke of the key is relatively small, it is difficult to adjust the location of the key sensor 89.
It is, therefore, an object of the invention to provide a key-touch state detection device for an automatic performance piano which has a simplified structure by having a sensor or sensors provided only on the hammer side and which can readily and accurately detect the key-touch state.